PowerToys/src/settings-ui/Settings.UI/MainWindow.xaml

<winuiex:WindowEx
    x:Class="Microsoft.PowerToys.Settings.UI.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="using:Microsoft.PowerToys.Settings.UI.Views"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:winuiex="using:WinUIEx"
    MinWidth="480"
    MinHeight="480"
    Closed="Window_Closed"
    mc:Ignorable="d">
    <winuiex:WindowEx.Backdrop>
        <winuiex:MicaSystemBackdrop />
    </winuiex:WindowEx.Backdrop>
    <Grid>
        <local:ShellPage />
    </Grid>
</winuiex:WindowEx>